We propose to investigate the biosynthesis of ACTH and the release of ACTH from the adenohypophysis and to determine the influence of CRF's, corticosteroids, and antimetabolites on these processes. The basic experimental system we will use is isolated adenohypophysial cells incubated in vitro. This system is a highly sensitive and accurate and apparently specific method of assay. Complete log dose response curves are employed to distinguish agonists from partial agonists among CRF(s). We plan to isolate and identify CRF(s) and to uncover antagonists of CRF. The isolated cell system offers a new approach to the understanding of the direct inhibitory actions of corticosteroids. The system offers a direct means of assessing the changes in responsiveness of pituitary cells to CRF. We are developing models to account for the diurnal rhythm and the episodic nature of adrenal cortical secretion in rat and man. ACTH equals Adrenocorticotropic hormone. CRF equals Corticotropin releasing factor.